Since the shrub recipe recently, I've been thinking in that sweet/sour direction. Use that recipe as a model, with your sweet base. You might have to strain out the fruit if you have large pieces, or drink with spoon in hand.

@AJ, what a great idea and I have filed it for my future blunders.

thanks everyone! i added lemon zest per amanda's suggestion in addition to the rhubarb and it's actually fabulous on my yogurt this morning. antoniajames, great idea about making a second batch - would have done that if i had extra sour cherries. sad, i was so excited for sour cherry jam and now the season's over. :( oh well!

You could probably cook down some frozen cranberries. Lot's of pectin in those.

Actually, I'd make a second batch with half the sugar and some extra lemon, and then mix the two, heat just to get them hot and then put them up for shelf stability. I've had problems in the past with stone fruit with wildly varying levels of natural pectin. Last summer I had one batch that set up much too firmly (plums) and another batch a few days later that ended up being much too loose (peaches). Neither problem was apparent until after they'd been in the jars for about a week. So I just opened up all the jars, emptied their contents into my jamming pan, cooked it to boiling, stirring well to combine, and then re-canned it, to produce some of the best jam I've ever made. I'm really not sure how it would work where sugar is the problem, however, because I don't know how important it is to the setting process for the type of jam you were making, but I'd certainly be willing to do an experiment to find out! (Trying to solve problems is a great way to gain knowledge you wouldn't otherwise.) And, in the future, if this ever happened to me, I'd take the jam off the heat as soon as I realized I'd put too much sugar in. I'd get the right amount of additional fruit to balance it back (putting the half-made jam in the fridge in the interim, if it were more than a few hours), and then I'd start from there, making a double batch -- or two halves of a double batch if I didn't have a wide, shallow jamming kettle. ;o)

The rhubarb was a good move! The only other thing I can think of is to add some flavors that would contrast with the sweetness -- like some brandy, lemon peel or even a dried chile. But your idea of just keeping it as a sauce to mix with tart yogurt makes sense, too. Anyway, I feel your pain -- been there!

sour cherry, and yes, i added some rhubarb for tartness. think it will turn into a super sweet sauce for yogurt rather than jam...

What kind of fruit is it, and do you have any other fruits available?